66 BRITISH APHIDES. 



Hypothesis No. 1 has the great disadvantage that 

 the young brood when hatched must be generally too 

 far removed from their natural food to make it pro- 

 bable that they would ever meet it. The ova also 

 would remain many months under ground during the 

 autumn, perhaps without development. 



No 2. — Migration to other plants certainly takes 

 place in several instances. Walker asserts it, with con- 

 siderable probability of the hop Aphis^ whilst the om- 

 nivorous character of the bean and the plum Aphis, 

 and also that of the wheat is very clear. Lichtenstein 

 states the same habit is assumed by Dy^yobius and 

 Scliizoneura. 



No. 3. — Dimorphism, with great change of economy, 

 has been conclusively proved in the vine pest, Phylloxera 

 vastatrix ; and there seems little reason for doubt that 

 persevering workers will prove a similar habit in other 

 genera. 



Thus, we may expect that some root-feeding 

 Aphides will be proved to be dimorphs of some well- 

 known aerial species; and conversely, that others 

 hitherto supposed to be strictly aerial, whose existence 

 has now been traced only to two or three months' 

 duration, wnll eventually be referred to subterranean 

 feeders with other specific names. 



These remarks are made as introductory to two 

 genera which are in a sense exceptional ; inasmuch as 

 some characters would ally them to the Lachnince, and 

 others to the Jphidince. Koch places Trama low in 

 the scale, even after Pemphigus. Passerini places 

 Trama and Paracletus amongst the Apliidince. If 

 these species should ever prove to assume wings, I 

 think it probable they will show the venation of 

 Laclmus. The character of their antennoa and laro-e 

 development of their rostra better also accord with 

 Laclmus than with Pemphigus, and therefore I here 

 place them in sequence. 



